The present invention relates to a test bench for testing a power transmission device, and to a test system comprising such a test bench provided with a power transmission device.
Although not exclusively, said test bench is more particularly intended for testing a transmission gearbox (main, intermediate or tail rotor) of a helicopter.
It is known that a test bench is generally used for carrying out two types of tests, that is to say:
development tests, the purpose of which is to simulate as closely as possible the real operating conditions (in particular the simulation of the rotor head loading pattern and the levels of load for a main transmission gearbox of a helicopter) of the power transmission device; and
acceptance tests, the purpose of which is to check the correct functioning of various mechanical components, subjected to a standard load spectrum (with measurements of torque, speeds of rotation and temperatures in particular).
In general, such a test bench, in order to test a power transmission device comprising at least one input shaft (for example an engine drive shaft or a power distribution shaft), an output shaft (for example a rotor shaft), and a casing, comprises:
a first assembly which is able to be connected to the output shaft of the power transmission device to be tested;
a second assembly which is able to be connected to the input shaft of the power transmission device to be tested and which is adapted, geometrically and kinematically, to said power transmission device; and
at least one transmission shaft connecting said first and second assemblies together.
Said second assembly is chosen according to the geometric and kinematic characteristics of the power transmission gearbox to be tested, in such a way as to provide:
on the one hand, a geometric adaptation with respect to said power transmission gearbox and in particular with respect to said input shaft or shafts, in such a way as to make it possible, in particular, to move said input shafts according to their usual degrees of freedom; and
on the other hand, a kinematic adaptation, to allow adequate functioning of the kinematic system formed by said test bench and the power transmission device mounted on the latter.
Consequently, when the type of power transmission device to be tested is changed, it is necessary to replace, on said test bench, said second assembly with a second assembly that is adapted (geometrically and kinematically) to the new power transmission device to be tested. Now, such a replacement operation is long and requires complex and costly tooling.
Furthermore, said second assemblies are very costly both to purchase and to maintain, in particular because they are generally manufactured as one-off items.
Furthermore, because of the diversity of existing power transmission gearboxes, it is necessary to provide a large number of such (different) second assemblies in order to satisfy the various possible demands for tests on one and the same test bench.
The present invention relates to a test bench making it possible to overcome these disadvantages.
For this purpose, according to the invention, said test bench for testing a power transmission device, in particular a transmission gearbox of a helicopter, comprising at least one input shaft, one output shaft and a casing, said test bench comprising:
a first assembly which is able to be connected to the output shaft of the power transmission device to be tested;
a second assembly which is able to be connected to the input shaft of the power transmission device to be tested and which is adapted, geometrically and kinematically, to said power transmission device; and
at least one transmission shaft connecting said first and second assemblies together, is noteworthy in that said second assembly comprises at least one subassembly comprising:
a first module provided with a mechanical unit that comprises gearing elements, which is adjustable in position and in orientation, and which is able to be connected to said input shaft of the power transmission device to be tested; and
a second module which is coupled with said first module and which makes it possible to provide a kinematic adaptation between said first module and said power transmission device to be tested.
Thus, by means of the invention, when the type of power transmission device to be tested is changed, it suffices:
to adjust said first module (of said second assembly) in position and in orientation in such away as to carry out the required geometric adaptation to make it possible to carry out the tests; and
to replace, simply and solely, said second module (of said second assembly), which is inexpensive and easy to replace (as described below), with a new second module which makes it possible to carry out the required appropriate kinematic adaptation.
Consequently, due to the invention, it is not necessary in this case to replace the whole of said second assembly, which makes it possible to overcome the aforementioned disadvantages.
Preferably, said second module comprises gearing having a reduction ratio which is adapted to that of the power transmission gearbox in order to obtain an overall ratio substantially equal to unity. Such gearing, of usual type, is of course inexpensive and easy to manufacture.
It is however not strictly necessary to obtain an overall ratio of 1/1. In fact, the torque-applying device of the bench is generally hydraulic and allows a certain sliding of the mechanical devices to which it applies the torque.
In a first embodiment, said second module is mechanically independent from said first module. It is then preferably produced in such a way as to serve as an interface between said first module and the input shaft of the power transmission device.
In a second embodiment, said second module is mounted, in a detachable manner, on said first module. In this case, said second module is uniquely connected to said first module (and no longer to the input shaft), which simplifies and facilitates the replacement of said second module.
Furthermore, advantageously, said first module comprises gearing elements making it possible to subject said mechanical unit:
to two rotations respectively about a vertical direction and about a horizontal direction located in a vertical plane which is transverse to the direction defined by the input shaft of the power transmission device to be tested; and
to a movement of translation along said horizontal direction of said vertical plane.
In general, the power transmission device comprises a plurality of n input shafts (for example one or more engine drive shafts and/or one or more power distribution shafts). In this case, advantageously, in order to be able to test this power transmission device, said second assembly comprises n subassemblies able to be coupled respectively to said n input shafts (n being greater than or equal to 2).
The present invention also relates to a test system comprising:
a test bench for testing a power transmission device, in particular a transmission gearbox of a helicopter; and
a power transmission device which comprises at least one input shaft, one output shaft and a casing and which is mounted on said test bench.
This system is noteworthy, according to the invention in that it comprises the aforementioned test bench.
When it is independent from the first module, said second module is preferably mounted on a detachable support also carrying the casing of the power transmission gearbox, which makes it possible to form a unit assembly (mechanically integrated support, second module and power transmission device) which can be easily removed and transported, in particular during a replacement.
The figures of the appended drawing will give a good understanding of how the invention can be embodied. In these figures, identical references denote similar elements.